Radionuclides naturally decay according to known and predictable decay chains, producing alpha, beta, and/or gamma emissions. Various systems and methods are known in the art for detecting and/or measuring each type of radiation. For example, scintillation detectors are highly sensitive to alpha, beta, and gamma emissions. In a scintillation detector, emissions produced by a sample interact with a scintillator to produce light pulses. A photomultiplier optically connected to the scintillator amplifies the light pulses and produces a signal corresponding to the occurrence and/or magnitude of each light pulse. A control circuit may supply power to the photomultiplier and/or process the signals from the photomultiplier to determine the presence and/or amount of radiation present in the sample.
A solid scintillation detector generally includes a light impermeable barrier that encloses the scintillator and photomultiplier to prevent the sample from contaminating the scintillator and to prevent exposing the photomultiplier to ambient light. Although gamma emissions can readily penetrate the barrier, low energy beta (i.e., less than approximately 1 MeV) and alpha emissions are not able to penetrate the barrier to reach the scintillator. As a result, solid scintillation detectors are not suited for detecting and/or assaying low energy beta or alpha emissions.
Liquid scintillation detectors, however, may be used to detect and/or assay low energy beta or alpha emissions. A liquid scintillation detector generally includes a liquid cocktail having a fluorescent material or scintillator in solution. Samples containing low energy beta and/or alpha emitters may be immersed in the liquid cocktail so that the beta and/or alpha emissions from the sample may interact with the fluorescent material or scintillator to produce light pulses. The light pulses may again be amplified by a photomultiplier and processed by a control circuit to determine the presence and/or amount of beta and/or alpha radiation in the sample.
Although portable solid scintillation detectors have been developed to enable remote monitoring for gamma and higher energy beta emissions, the components included in liquid scintillation detectors have heretofore resulted in larger and heavier detectors than solid scintillation detectors, limiting the ability to remotely monitor for low energy beta and alpha emissions. As a result, a portable system and method for assaying low energy beta and/or alpha emissions would be useful.